Synthesis of Pyrazole Derivatives for TLC-FAPA

All reagents used were commercial products. Ethyl 2,4-dioxovalerate, hydrazine hydrate, 2-hydrazinopyridine, 2-hydrazinobenzothiazole, lithium aluminum hydride, nicotine, sparteine, and anhydrous tetrahydrofuran (THF) were obtained from Sigma-Aldrich (St. Louis, MO, USA). Anhydrous ethyl alcohol and all other solvents were of p.a. grade, obtained from Avantor Performance Materials Poland S.A. (Gliwice, Poland) and were used without further purification. The commonly used analgesic, consisting of paracetamol, propyphenazone, and caffeine, was obtained from the local pharmacy.
Synthesis of pyrazole derivatives used in this work as analytes for the TLC-FAPA technique has been described in detail in our previous publication [25 (link)]. For all TLC-FAPA experiments, the Merck Millipore TLC silica gel 60 F₂₅₄ aluminum sheets was applied.